breech plug

[rkeltner]

i am (slowly) working my toward building an underhammer express rifle in 45 caliber. i have finally located a local gunsmith who can do my bteeching. my problem is with something he said about the size of the plug, since he said a 1/2" plug would be strong enough for what i want(i will be using 5/8 regardless of what he says). soooo, what do the muzzleloader gurus on this site say to that advice?

 

[ResearchPress]

This does not answer your question or refer to underhammers, nonetheless it may be of assistance/interest. See Breech Plugs on the Long Range Muzzle Loader web site.

David

 

[shortstring]

I make all of mine .550 deep. These are custom lathe turned threads that fit proper. It's not likely that you will make yours too strong. If you are using a patent breech the threads will be ahead of the nipple & the depth of threads will not be much of a factor. If the nipple is in front of the threads then the length of hammer will dictate the length of the threads.

Paul

 

[rabbit03]

i am (slowly) working my toward building an underhammer express rifle in 45 caliber. i have finally located a local gunsmith who can do my bteeching. my problem is with something he said about the size of the plug, since he said a 1/2" plug would be strong enough for what i want(i will be using 5/8 regardless of what he says). soooo, what do the muzzleloader gurus on this site say to that advice?

I would imagine that there are several factors to consider when making a breech. For example, barrel thickness, caliber, plug or pattent breech, etc..

Why not ask our local resident expert in this field your question?? He is here on the Forum and I am sure would help you answer your question.

John L. Hinnant, my good friend who wrote the BOOK, is the one I get to do all of my work and for advice. His machine work is better than I can shoot! :hatsoff:


[url] http://www.trackofthewolf.com...=4&SUBID=38&STYLEID=135&PARTNUM=BOOK-CIG-PRBF[/url]

rabbit03

 

[Mike Brooks]

1/2" is plenty.

 

[rkeltner]

i'm realizing that i didn' specify that the gunsmith was talking about diameter, not length length is dictated by action design(in this case, about 1.5"). this gunsmith was talking about using a 1/2-20 thread plug.

 

[LRB]

I agree with Mike on length. 1/2" is plenty. Many originals were only 3/8" long.

 

[JOHN L. HINNANT]

Good Morning Fixit,

Since Rabbitt has thrown my name into the mix, I will offer my advice on the breeching question.

To begin with, I will throw the bacon grease into the fire and state that I do care what standards were used by the old timers.

My work is machined in accordance for today's standards of safety. The standard for MINIMUM HOLDING STRENGTH of a threaded fasterner is the length of thread equal of the diameter of the thread.

Now specifically to your question. If your barrel size accoss the flats is 15/16" or 1", a 3/4-16 TPIwould be the proper size. In the case of a 15/16" barrel in 45 caliber, a 5/8-18 TPI would be satisfactory.

The Thompson-Center folks use a 11/16-20 TPI size which is in the neither the NC nor the NF standardardized thread family, but is in the standardized SPECIAL THREAD SERIES.

For my part, I like the 11/16-16 TPI NF thread for most (but not ALL) 15/16's barrel breech jobs. Caliber or bore size is also a prime consideration in selecting the appropriate breech plug size.

It is impossible to tap a complete thread to the bottom of a blind hole or the breech of a muzzle loading loading rifle. the end of the breech plug threads will have to be relieved from one to one and a half thread length. This means that the MINIMUM holding strength has been reduced.

To compensate for this, make the breech plug thread 1/8" or 3/16" longer or even a 1/4 inch longer.

The longer breech plug will not be a problem even with a shorter hammer throw. The end of the breech plug can be pre-drilled for a short powder powder chamber. It is best to finish the powder chamber with a ball end mill of the same diameter as the twist drill. This will give the end of the powder chamber a very nice, professional finish and appearence.

The barrel can then then be drilled and tapped through the barrel AND breech plug at the vary end of the powder chamber.

A good machinist can even taper the powder chamber to form a Nock type of powder chamber.

And by the the way, instruct your machinist to BORE not DRILL the breech to the correct tap drill diameter in order to form an internal square shoulder for the end of the breech plug to mate against.

If he tells you this is not necessary or worth the extra trouble, find yourself another machinist.

The part of the breech plug that fits in to the under hammer action does not have to be the same diameter as the the breech plug thread.

These are my personal views on breech plug safety, and I will not engage in a debate on that issue.

Best regards and good shooting.

God and Texas

John L. Hinnant

If you are not an NRA or NMLRA Member, why not? I am carrying your load.

 

[rkeltner]

i like the way you talk, mr. Hinnent. i'm a production machinist, so it annoy's me when someone throws me advice that doesn't quite wash, but you are shooting very straight. it may be a while before i am actually ready for the breeching, but i have a feeling i will be shipping to you for the work. thanks much, and keep shooting straight!

 

[JOHN L. HINNANT]

Greetings Fixit,

I mis-stated my position about old time standards and safety standards of today.

It should have read "I do NOT care......"

Best regards and good shooting,

God and Texas,

John L. Hinnant

 

[buffler]

FWIW, John, Your info is right on the mark!
Don